Talking about best season to visit Lahaul Spiti Valley and Leh Ladakh crossing high mountain passes, first we need to know briefly about about climate of the terrain, Spiti and Leh are the Landscapes, which open their doors for just few months in a Year. You can traverse through the circuits only from End of the May till Mid of October.

Route from Shimla to Kaza is mostly opened throughout a year but Route from Manali to Kaza is opened for Just 5 months in a year and same is the case if you want to cover other geography of Leh Ladakh.

As per experience of most, September is the best Month to visit the Spiti Valley Circuit.

Reasoning for this is below:

1. At the end of the May and mostly beginning of June, high Mountain Passes open their gates to these places. For both the circuits the critical Pass is Rohtang Pass and then there are other High Passes like Kunzum La Pass for Spiti Valley and Khardung La Pass, Barlachala Pass etc on the route to Leh Ladakh. May till June and early July is a period when Ice at high mountains melt and streams would be roaring full of water, making it more difficult to cross those. Also if you have to cover the plains, heatwave during the period would suck energy out of you while riding in plains

2. July till end of the August, is a period of rains and Monsoon and it is never advisable to ride in such terrain in rains.

3. Month of September: This is the month when most the Ice is already melt and streams are almost dried up and also riding in plains is also not very harsh as weather becomes favorable to go out.

4. October till road closes: There can be a snowfall anytime in October and a risk of route getting closed and high places getting isolated and disconnected for days. Go there at your own risk in October.